The present invention relates to digital data processing and, particularly, to the visualization of three-dimensional and higher-dimensional images in two-dimensions, e.g., on a two-dimensional display screen. The invention has application, by way of non-limiting example, in medical imaging, microscopy, and geosciences, to name but a few.
Three-dimensional (3D) volumetric images (also referred to as stacks of 2D images) occur in many disciplines like medicine, geosciences, or microscopy. Such 3D images can be acquired using machines like computer tomographs, magnetic resonance imaging devices, or confocoal microscopes, or they can be the result of computation.
The visual perception of natural 3D density distributions, like clouds or fire, involves projection onto a 2D plane, the retina. This process can be mimicked using a computer in order to compute a 2D projection of a 3D image and to display that on the computer screen, thus simulating the perception of true physical 3D objects. The 3D image, represented as a scalar function on a 3D volume, can be visualized in a number of ways, for example, by color contours on a 2D slice or by a polygonal approximation to a contour surface. A set of such visualization techniques, commonly known as direct volume rendering, produces a 2D projected image directly from the volume data without intermediate constructs.
Direct volume rendering of a 3D image typically requires some model of the optical properties of that volume, e.g., how the data volume emits, reflects, and scatters light. That model is utilized to compute a 2D projection image, e.g., by evaluating the integrated effects of the optical properties along viewing rays corresponding to pixels in the 2D image. Such evaluations can be very computation intensive, especially for large 3D volume image data.
An object of this invention is to provide improved methods and apparatus for digital data processing and, more particularly, by way of non-limiting example, for image visualization.
More particular objects of the invention are to provide such methods and apparatus as facilitate visualization of three- and higher-dimensional images. A related object is to provide such methods as facilitate such visualization in two-dimensions, e.g., as on a two-dimensional display screen.
Yet further objects of the invention are to provide such methods and apparatus as can be implemented at lower cost. And, a related aspect of the invention is to provide such methods and apparatus as can be implemented using standard, off-the-shelf components.